The head of the U.N. nuclear agency says he has signed a joint statement on future cooperation over Iran's nuclear program. Yukiya Amano arrived in Tehran shortly after Iran and six world powers failed to reach agreement on curbing Iran's nuclear program. NPR's Peter Kenyon is following the nuclear story and has this report.

PETER KENYON, BYLINE: Amano tells reporters in Tehran that he hopes the new agreement can be implemented within three months. He says it includes allowing inspectors to visit at least two sites of interest, the Gachin uranium mine and the heavy water reactor at Arak. The IAEA track is essentially separate from the negotiations between Iran and the so-called P5+1 - the U.S., Britain, France Germany, Russia and China.

But there is some overlap, including questions about the heavy water reactor. In addition, if there is to be an agreement, verification will play a large part, and that will fall to the IAEA. Despite the outstanding questions, the agency already spends a lot of time inspecting nuclear sites in Iran. In a recent interview with NPR, Herman Nackaerts, the recently retired deputy head of the IAEA, said people may not realize how frequently inspectors are on the ground.

HERMAN NACKAERTS: Well, the agency is currently inspecting 17 declared facilities in Iran. So every single day of the year the agency has between two and six inspectors on the ground in Iran.

KENYON: Every day?

NACKAERTS: Every day of the year.

KENYON: Negotiators for the P5+1 and Iran will create even more work for the inspectors if they manage to strike an agreement to restrict Iran's program in exchange for limited sanctions relief. Three grueling days of talks in Geneva ended early Sunday morning without an accord. How the talks failed is still being explored.

Reports from Israel, which gets regular briefings on the talks from the U.S., quote a senior American official as saying Iran was the one that walked away from the table and that there is a disagreement over Iran's desire for a recognized right to enrich uranium. Iranian officials say it was a hard line by France that prevented an initial agreement in Geneva.

After the talks concluded, U.S. Secretary of State John Kerry praised France's contribution and said more talks will make any deal stronger.

SECRETARY OF STATE JOHN KERRY: I think it's good we're going to take the time we're taking, to make certain that we are dotting the I's and crossing the T's and doing what is necessary to have an agreement that we are assured we can look our allies and our friends in the face and say this gets the job done.

KENYON: The two sides will return to Geneva on November 20, with Iran's Foreign Minister Mohammad Javad-Zarif saying with a little more hard work an agreement can be struck. Israeli officials have vowed to use the coming days to press their case for demanding a halt to all uranium enrichment in the interim stage of any agreement. Members of Congress, meanwhile, are mobilizing for a push to enact even more sanctions against Iran, which officials say could be harmful to the talks.

Longtime arms control expert Robert Einhorn says given the long history of mistrust between the U.S. and Iran, there's no guarantee that a final agreement can be reached. But he says getting a first-step agreement that allows the sides to at least try for a comprehensive deal may be possible.

ROBERT EINHORN: But if you're talking about getting P5+1/Iranian agreement on this two-part framework, this specific first step, and the broad outlines of a comprehensive deal, I think that is possible. I think it's possible even this year.

KENYON: But if the talks fail, whether because of substantive differences or pressure from critics, analysts say an important opportunity to resolve this long-running problem may be lost for years to come. Peter Kenyon, NPR News, Istanbul. Transcript provided by NPR, Copyright NPR.